This invention relates to fingerprint processing. More particularly, this invention relates to the capture of fingerprints from generally inanimate objects. The invention is particularly useful in the science of forensics.
For the past 100 years, law enforcement agencies have collected human fingerprints from crime scenes in order to identify the perpetrators of various felonious crimes from petty larcenies to murders. In the past, the fingerprints were discovered at the scene and crime scene technicians would apply powders to the prints, which are actually human skin oils that are deposited on the evidence. The skin oils would adsorb the powder and become whitish in color, which allowed for either photography or removal from the evidence with adhesive tape. From the crime scene, the latent prints would be taken to a lab, photographed, categorized, and then compared visually by skilled technicians to vast quantities of prints on file. This procedure was followed in order to locate a match, thereby identifying a suspect.
Modern forensic science has improved upon this process immensely. Fingerprint identification is done now by using sophisticated computer programs run by main frame computers in such centers as the FBI fingerprint labs in Washington D.C. Manual inspection of card files is almost a thing of the past. The computers use scanning technology to read fingerprint evidence from prepared samples and automatically categorize and match the prints to corresponding prints stored in a database.
One problem that needed to be overcome to enable the law enforcement agencies to implement this system was that the latent fingerprint itself is a very fragile object. A powdered fingerprint could be easily smeared which could render it useless for comparison to known prints. Also, fingerprints are generally very faint, which led to many prints not being found in the first place. Even with the adhesive tape method, fingerprint removal from the crime scene to the lab was tenuous at best. A method was needed to enable the forensic technicians to find all fingerprints, improve the contrast between the prints and the surrounding surfaces, harden the prints so that smearing is less likely and transport from site to site is possible.
The answer was found to be a development process using fuming cyanoacrylate ester. Cyanoacrylate ester is a cyanide compound that has superior adhesive properties, especially for human tissue. It is commonly sold under trade names such as SuperGlue. As most people know, when cyanoacrylate ester is applied to two skin surfaces which are then brought into contact, the skin surfaces fuses and stick together. The result can range from merely annoying, if two fingers are fused, to extremely dangerous, if an eye membrane and skin are involved. The adhesive property of cyanoacrylate esters is so well known that medical researchers are investigating the possibility of using the compound to replace sutures in closing of wounds and incisions during operations.
Forensic scientists used this property of fusing and hardening skin oils to their advantage by heating the liquid cyanoacrylate ester and causing a mist or vapor to be formed. This vapor deposits on the latent fingerprint oils, hardens them and turns them whitish in color. When dry, the print treated by vaporous cyanoacrylate ester is very resistant to smearing, fixed to the substrate and is easily seen against a darker background. In addition. if the entire piece of evidence, such as a plastic garbage bag, gun or knife is subjected to the fumes, all fingerprints which are on the evidence will be developed and will stand out visually, reducing the possibility of losing fingerprint evidence. After developing, fingerprint evidence is processed further, allowing scanning into a computer for comparison and identification, all by techniques that are now well-known to the art.
This method has been utilized for many years with excellent results and is now the state of the art for fingerprint processing. However, some detriments are also inherent in this method.
When the cyanoacrylate ester is heated, a white vapor or mist is formed. The particle size of the vapor is very small and is easily respirable. When inhaled, the small particles can migrate into the small pulmonary channels of the lungs and cause irritation or other lung reactions that are deleterious to lung tissue. As importantly, when cyanoacrylate ester is heated, the possibility of compound breakdown exists wherein hydrogen cyanide is formed and is present in the vapor. It is well known to health experts that hydrogen cyanide (HCN) is toxic and dangerous to human health. Inhaling this compound is to be avoided.
Products have been developed to contain the vapors of cyanoacrylate ester and offer some degree of protection for the user. Generally, the design of these items is similar to laboratory fume hoods or glove boxes, wherein the evidence is placed, the sash or door closed, the liquid cyanoacrylate ester is fumed, misted, or vaporized and the fingerprints are processed. At the end of the deposition phase, the fumes are vented via a fan to an outside exhaust. By definition, this type of chamber is fixed in location, usually in a laboratory environment. Since solid connection to the ductwork is required, portability within the lab or from the lab is not possible. Also, all of the vapors are expelled to the atmosphere, increasing pollution levels emitted in the lab exhaust. If higher levels of HCN are present, a potential safety hazard is incurred since the HCN is traveling throughout the lab""s ductwork.
If the process is being carried out in the field, a portable enclosure, in some cases an inverted fish tank is used to contain the vapors. At the end of the fuming cycle, the chamber is simply lifted off and the vapors are allowed to dissipate in the atmosphere. Of course, a breeze or wind could blow the vapors back into the face of the technician or deposit the vapors on other surfaces such as car paint or such.
All of these solutions, however expedient, are not fully safe, nor are they automated in any way. Technician training and experience is very critical to the fuming process, in that too much or to little cyanoacrylate ester fumes or processing time could destroy the fingerprints and therefore important case evidence. This user dependence is compounded by the realization that the fuming process is also temperature and humidity dependent, in that it is well known that best results are obtained at about 80% RH at 72 F. Control (or at least measurement) of these parameters would allow for more consistent processing.
An object of the present invention is to provide an improved apparatus and/or method for capturing a fingerprint from an object.
A more particular object of the present invention is to provide such an apparatus and/or method which is portable.
Another particular object of the present invention is to provide such an apparatus and/or method which has enhanced safety features.
An additional object of the present invention is to provide such an apparatus or method which facilitates optimal deployment of a chemical fingerprint fixative agent such as cyanoacrylate ester.
A further object of the present invention is to provide such an apparatus or method which is easy to use owing in part to automatic operation.
These and other objects of the present invention will be apparent from the drawings and descriptions herein.
An embodiment of a fingerprint capture or processing apparatus comprises, in accordance with the present invention, a casing defining a sealable chamber, a first support in said chamber for holding a source of a chemical fingerprint fixative agent, a second support in said chamber for holding an article to be tested for fingerprints, a filtration system connected to said chamber for removing contaminants from air in said chamber, and an air circulation assembly operatively connected to said casing for circulating air from said chamber and through said filtration system.
In accordance with another feature of the present invention, the fingerprint capture or processing apparatus further comprises a humidity control device connected to the air circulation assembly for modifying a humidity level in the chamber to a predetermined relative humidity. It is contemplated that the humidity control includes a humidity sensor or measurement device disposed in operative communication with the processing chamber. The humidity modification may be effectuated in part by an ultrasonic humidifier device.
In accordance with an additional feature of the present invention, the air circulation assembly includes ductwork defining a first path for directing air from the chamber through the filtration system and ductwork defining a second path bypassing the filtration system for guiding air from the chamber. The second pathway is used, for example, to circulate air through the processing chamber during a humidity adjustment process prior to a delivery of a chemical fixative agent to the processing chamber. The air circulation assembly may include a first fan or blower for moving air along the first path and a second fan or blower for moving air along the second path.
Pursuant to a further feature of the present invention, the air circulation assembly communicates with the fingerprint processing chamber near an upper end and a lower end thereof, whereby air from the chamber may be filtered or cleaned by the filtration system and subsequently returned to the chamber.
A perforated plate may be suspended from sidewalls of the casing over the first support, thereby dividing the chamber into an upper compartment and a lower compartment. In that case, the air circulation assembly is connected to the casing at the lower compartment for blowing cleaned air into the lower compartment.
Where the casing includes a door for enabling access to the chamber, the fingerprint capture or processing apparatus further comprises a contaminant sensor in operative communication with the chamber for monitoring quality of air in the chamber, and a lock mounted at least indirectly to the casing for locking the door. The lock is operatively connected to the contaminant sensor for enabling opening of the door only when the chamber is effectively void of contaminant particles.
A heating element is disposed in the fingerprint processing chamber for heating the fingerprint fixative agent during a beginning phase of a fingerprint detection procedure.
In accordance with additional features of the present invention, at least one timer is operatively connected to the air circulation assembly for determining air purge and recycle periods, while the casing includes at least one transparent panel, whereby an operator can monitor an extent of fingerprint fixation.
A method for processing objects for fingerprints comprises, in accordance with the present invention, placing an article to be tested for fingerprints into a chamber, thereafter sealing the chamber, introducing a chemical fingerprint fixative agent into the sealed chamber, cleansing or filtering air in the chamber to remove particles of the chemical fingerprint fixative agent after fixing of fingerprints on the article by the chemical fingerprint fixative agent, preventing access to the chamber after the sealing thereof and prior to the removal of the particles of the chemical fingerprint fixative agent from the chamber, and enabling access to the chamber by an operator only after cleansing or filtering of air in the chamber to effectively remove particles of the chemical fingerprint fixative agent.
A method in accordance with the present invention facilitates fingerprint capture while simultaneously protecting personnel from biologically dangerous or deleterious chemicals used in the fingerprint fixation process. The chemicals are filtered from the air of the chamber prior to the opening of the chamber after a fingerprint capture process. Access to the chamber is prevented during the fingerprint capture or fixation process, prior to removal of effectively all particles of the chemical fingerprint fixation agent.
Where the placing of the article into the chamber includes opening a door to the chamber, the article is inserted through the opened door into the chamber, and the door is subsequently closed, while the sealing of the chamber includes locking the door to prevent an opening of the door prior to the cleansing or filtering of air in the chamber.
The cleansing or filtering of air in the chamber includes circulating air from the chamber through a filtration system. Preferably, the cleansing or filtering of air in the chamber further includes returning air to the chamber after the circulating of the air through the filtration system.
A fingerprint capture apparatus and method in accordance with the present invention facilitates the capture of fingerprints by a forensic scientist or technician in part by providing easy access to the processing chamber (where the access door is a front panel of the casing) and in part by providing safety features which protect the user from the cyanoacrylate ester vapors. In addition, a fingerprint capture apparatus and method in accordance with the present invention enables the measuring and/or control of internal temperature and humidity, thereby optimizing the generation and application of cyanoacrylate ester vapors. A fingerprint capture apparatus and method in accordance with the present invention is easily portable within or from a lab and ensures removal of all contaminants from the fingerprint capture or processing chamber before venting of the air from that chamber to the lab or atmosphere. Moreover, a fingerprint capture apparatus and method in accordance with the present invention may incorporate control logic to adjust and control the length of time of purge cycles, fuming cycles and cyanoacrylate ester vaporizer heater elements.